1. Field of the Invention
The present invention relates to a copper material used for chemical vapor deposition (hereinafter abbreviated as CVD) and a process for forming a copper-containing thin film using the same. More particularly, it relates to a CVD material comprising a xcex2-diketonatocopper (II) complex which is liquid at room temperature and a process for forming a copper-containing thin film using the CVD material.
2. Description of the Related Art
Copper and copper-based alloys have been applied as a wiring material of LSI for their high electrical conductivity and elecromigration resistance. Complex oxides of copper are expected for application as functional ceramic materials, such as high-temperature superconductors.
Techniques for making a copper-containing thin film of copper, copper-containing alloys, complex copper oxides, etc. include sputtering, ion plating, and pyrolytic coating, and the like. In particular, a CVD technique has been given studies as the most suitable thin film formation technique because of superior performance in composition control, step coverage, and planarization and adaptability to the LSI process.
However, the CVD materials that have hitherto been proposed for forming a copper-containing thin film by CVD do not always possess sufficient characteristics. For example, xcex2-diketonatocopper (II) complexes typified by dipivaroylmethanatocopper, being solid, need be gasified through sublimation or be maintained at a high temperature at or above the melting point in the vaporization step. As a result, the amount of vapor produced is insufficient and changes with time, posing problems in raw material gas supply and in-line delivery of the raw material. To solve the problems, a solution CVD method using a solution of a solid material in an organic solvent has been proposed, e.g., in Japanese Patent Laid-Open Nos. 5-132776 and 8-186103. However, the dissolved solid material is likely to precipitate due to temperature change in the vaporization unit, partial volatilization of the solvent or concentration change of the solution. As a result, the feed of the solution tends to decrease with time due to, for example, the precipitate clogging the feed pipe, resulting in instability of film forming rate and film composition.
Japanese Patent Laid-Open Nos. 10-140352 and 10-195654 teach use of a copper compound comprising a xcex2-diketonato complex of copper (I), which is liquid and highly volatile, having added thereto an organosilicon compound. This compound is thermally and chemically labile and decomposes in low temperature and therefore unsuited for use in a multi-component system.
U.S. Pat. No. 5,980,983 discloses use of a liquid xcex2-diketonate material prepared by mixing two or more kinds of xcex2-diketones. Being a mixture, the material is associated with the problems of process instability and precipitation.
An object of the present invention is to provide a copper material for CVD which is a single liquid compound having stability enough for application to various CVD techniques and a process for forming a copper-containing thin film by CVD using the copper material.
As a result of extensive investigation, the present inventors have discovered a liquid xcex2-diketonatocopper (II) and ascertained that the above object is accomplished by using this compound.
The present invention, having been completed based on the above finding, provides a material for CVD comprising a xcex2-diketonatocopper (II) complex which is liquid at room temperature.
The present invention also provides a process for forming a copper-containing thin film on a substrate by CVD which comprises using the above-described material.
The present invention provides a copper material for CVD which is liquid and has sufficient stability applicable to various CVD techniques and a CVD process for forming a copper-containing thin film using the material.